A Happy Pig

Is utilitarianism is “a doctrine worthy only of swine” [J.S. Mill Utilitarianism (1863) p. 332]. Is it better to be Socrates dissatisfied than a pig satisfied? Or is an impartial utilitarian concern for non-human sentience another argument in its favour?
The non-human animals we factory-farm and butcher are functionally akin to human babies and toddlers in their capacity to suffer. A fondness for the taste of human flesh is not reckoned a compelling moral argument for cannibalism. By parity of reasoning, to abuse and kill our fellow creatures because we like the taste of their flesh is morally indefensible too. For pigs, like small children, ought to be happy.